Baskets for centrifuges



United States Patent 3,507,394 BASKETS FOR CENTRIFUGES Albert Moore, Chesterfield, Derbyshire, England, assignor to The Birmingham Small Arms Company Limited, Birmingham, England, a British company Filed Mar. 13, 1969, Ser. No. 806,986 Claims priority, application Great Britain, Mar. 19, 1968, 13,183/ 68 Int. Cl. B04b 3/00 US. Cl. 210380 5 Claims ABSTRACT OF THE DISCLOSURE A frusto-conical wire screen centrifuge basket comprises a plurality of curvilinear wires extending between the open and closed ends and supported by annular hoops. These wires are of changing shape, preferably of involute form, intermediate the basket ends, the angle which each Wire makes with a perpendicular between the ends progressively increasing in such manner that the wires are parallel throughout their lengths.

This invention relates to baskets for centrifuges of the kind suitable for use in the separation of liquids from granular materials, for example, the separation of water from Wet small coal and coal slurries.

Usually such baskets comprise a plurality of wire screening panels assembled together to form a basket of frusto-conical shape having its largest diameter at the open end, and having a substantial part attached to the other ends of the panels thereby forming the closed end. The wires employed usually have a substantially triangular or wedge-shaped cross-section and wires of this kind will hereinafter be referred to as wedge-wires. The baskets are usually adapted to rotate about a vertical axis but sometimes they are adapted to rotate about a horizonal axis.

To obtain uniform screening the wedge-wires are usually arranged parallel to each other in each panel, but due to the tapering shape of the panels the wires approach one or both sides of the panel at an angle. The wedge-wires are usually welded at their ends, but the welds between the sides of the panel and the wedge-wires at an angle thereto sometimes tend to be weak and eventually holes may form in the basket at these points. Our Patent No. 1,041,304 described a construction in which the wires were parallel with each other and with the side of each panel, thereby avoiding the disadvantages flowing from the use of panels with tapering sides as above explained. The object of the present invention is also to avoid the same disadvantages in an alternative or improved manner.

According to the invention a wire screening basket of substantially frusto-conical shape comprises a plurality of curvilinear wires supported by annular members, the angle which said wires make with a perpendicular line between the edges of the basket progressively increases from the smaller to the larger diameter of the basket in such a manner that the wires are substantially parallel throughout their length.

Preferably each Wire extends over the screen surface, from the closed to the open end, substantially in the form of an involute curve.

An embodiment by way of exemplification of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view of a basket constructed in accordance with the invention,

FIG. 2 corresponds to FIG. 1 in showing the development of a curved wedge wire, and

3,507,394 Patented Apr. 21, 1970 FIG. 3 is a cross section of a number of the wires.

The basket comprises a plurality of wires 1 in the form of hoops uniformly spaced in parallel longitudinal relationship, each wire progressively increasing in diameter to give the taper required for the frusto-conical shape, with the smaller diameter hoop adjacent a circular plate 2 constituting the closed end of the basket, and the larger diameter hoop the open end of the basket.

Around the circumference of the plate 2 are secured one end of a plurality of wires 3 which extend over the surfaces of the hoops 1 and terminate at the hoop of larger diameter, the wires 3 and hoops 1 also being secured together to form a frusto-conical screen. The basket structure is completed by upper and lower shedding rings 4 and 5 attached to the periphery of the screen. The securing of the wires and hoops in the fabrication of the basket may be effected in any suitable manner, but is preferably by the use of projection welding.

The wires 3 of uniform cross section, as shown in FIG- URE 3, constitute wedge wires extending over the surface of the screen from the closed to the open end of the basket, each wire being of a curvilinear form such that the wires are substantially parallel to each other and the space therebetween constant.

Since the diameter of the basket increases from one end to the other, the circumferential pitch, that is the circumferential distance between like parts of the wires on a plane parallel to the smaller diameter, closed end of the basket, must increase in substantially direct proportion to the diameter of the basket on that plane. This relationship can be expressed by the formula where D is the diameter of the basket at any distance from the closed end of the basket, d is the smallest diameter of the basket, P is the circumferential pitch at diameter D and p is the circumferential pitch at diameter d.

FIGURE 2 indicates the circumferential pitch at the equally spaced hoops 1 of an exemplary basket. In order to achieve the indicated circumferential pitch at any hoop while maintaining the wires 3 in substantially parallel relationship the wires cross the hoop at a predetermined angle. For example, the wires cross the hoop which is the second from the closed end of thebasket at an angle of 16 39, which angle results in the circumferential pitch at that hoop being 2.610 mm. Thus the pitch of the wires measured perpendicular to their center lines remains 2.500 mm. although measured circumferentially at the above mentioned hoop the pitch is 2.610 mm.

A basket constructed in accordance with this invention from the development data given in FIG. 2 would have a sufficient number of hoops for adequate strength and a calculated number of wedge wires to form a frustoconical basket having a predetermined size of uniform screen aperture, a suitable jig being untilised to hold the hoops and wires in the predetermined positions prior to welding.

What I claim is:

1. A wire screening basket of substantially frusto-conical shape comprising a plurality of curvilinear wires extending between opposite ends of said basket and supported by annular members, the angle which said Wires make with a perpendicular line between the ends of the basket progressively increasing from the smaller to the larger diameter of the basket in such a manner that said wires are substantially parallel with each other throughout their lengths.

2. A basket according to claim 1, wherein the wires are preformed to the required curvilinear form.

3. A basket according to claim 1, wherein the curvilinear wires are of substantially involute form.

4. A basket according to claim 1 wherein additional annular support members are positioned intermediate support members at the open and closed ends of said basket. 5

5. A basket according to claim 1, wherein said annular members are parallel hoops fixed to said wires intermediate opposite ends of the baskets.

4 References Cited UNITED STATES PATENTS 9/1957 Van der Molen 210-380 10/1959 Heckmann et a1. 210380 JAMES L. DECESARE, Primary Examiner 

